Outdoor electrical systems need to conform with regulatory provisions to ensure safe and reliable operation in the presence of inclement weather. The outlet boxes and junctions and outlets are particularly prone to moisture conditions, and great care is taken to provide sealed construction. Gasketed cover plates are provided to seal the box cavity. Threaded ports receive rigid threaded conduits to protect against moisture entry at the electrical lines. Currently, commercially available boxes for outdoor use are provided for accepting only a single threaded conduit size. This presents problems for both the supplier and installer. The supplier must carry inventory and devote space for each size. The installer must carry both sizes inasmuch as the complete details of a job might not be fully defined at time of purchase. There are also situations, where due to design conditions or revisions, multiple conduit sizes are presented at a junction or outlet. If a larger conduit is required, the outlet box must be replaced. Where a smaller conduit is required, separately procured reducer bushings are available to handle the size reduction. This provides versatility for the installer, but further complicates supplier inventory.
Available reducer bushings are cylindrical sleeves provided with internal and exterior threads. For assembly, the installer manually threads the bushing into the outlet port, and thereafter threads the conduit into the bushing. To ensure a tight fitting, the installer often uses a wrench for final tightening resulting in a tightly seated condition with the bushing. Should the conduit need to be removed for repair or system modification, difficulties can arise. The breakaway torque at the conduit/bushing interface due to excessive installation force may be greater than the breakaway torque at the bushing/outlet box interface. Accordingly, the bushing rotates with the conduit, and remains attached after conduit removal. Removal of the bushing requires a wrench, which can damage the threads and prevent reuse of the bushing, and in practice both the conduit and bushing are discarded requiring new materials for completing the modification.